JPH1191237A - Inkjet recording sheet - Google Patents

Abstract

(57) [Problem] To provide an ink jet recording sheet excellent in anti-counterfeiting which does not require a special device and can be authenticated by a simple method. A paper support on which optical density is partially formed is used as a support for an ink jet recording sheet. Optical shading is provided by the following four methods.
(1) Transparent paper is used as a support. (2) Printing using white ink on the surface of the paper support. (3) A paper support having a three-layer structure is used in which a paper support is attached to both sides of a paper on which a cut coloring film piece or a cut metal foil piece is ground.
(4) A cut coloring film piece or a cut metal foil piece is sandwiched between a two-layer paper support and an adhesive to form a support.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, and more particularly, to an ink jet recording sheet having improved anti-counterfeiting properties by partially forming optical shading on a support. is there.

[0002]

2. Description of the Related Art Ink-jet recording is a method in which fine droplets of ink are made to fly and adhere to a recording sheet such as paper according to various operating principles, thereby recording images and characters. It has features such as easy multi-coloring, great flexibility in recording patterns, and no need for development-fixing. It has rapidly spread in various uses as a recording device for various figures and color images including Chinese characters. I have. Further, an image formed by the multi-color ink jet system can obtain a record comparable to multi-color printing by a plate making system or printing by a color photographic system. In addition, in applications requiring a small number of copies, it is being widely applied to the field of full-color image recording because it is less expensive than the photographic technique.

In general, such an ink jet recording system has advantages that an image can be obtained by a relatively simple apparatus, maintenance is easy, and no noise is generated. It is widely used in a wide range of fields such as computer terminals, label printing machines, vending machines such as ticketing machines, and the like. In particular, when applied to uses such as tickets, voting tickets, securities, receipt documents, etc., it is desired that the authenticity of issued tickets can be easily confirmed.

Some proposals have been made to make paper most commonly used for these various kinds of cash vouchers have a forgery prevention technique. For example, JP-A-6-108339 discloses that when a paper web is formed on a fourdrinier wire, preferably, a viscous aqueous solution containing a dye or a fluorescent dye is jetted from a nozzle before a dry line. A security paper provided with a transparent pattern is presented. For this purpose, it is also well known that fine and precise tint block printing is performed on the surface of these cash vouchers. However, in any of these methods, since a unique pattern that can be visually identified is provided on the surface of the paper in any case, the surface of the paper is not in a blank state, and the degree of freedom of inkjet recording is impaired. Further, in the former case using a fluorescent dye, a special device such as a black light and a dark box is required for authenticity determination.

[0005] Furthermore, as for the ink jet recording sheet, the absorbability and fixability of the ink jet ink are also important. That is, from the features such as high printing speed, low noise, easy multi-color, development-fixing is unnecessary, in the ink jet recording apparatus that has spread, ink jet ink that is difficult to dry is used to avoid nozzle clogging, The components of the ink are binders, dyes, solvents, and the like dissolved in water,
That is, a water-based ink is generally used. Therefore, the recording sheet has a high density of print dots, a bright and vivid color tone, and has a high ink absorption, so that even when the print dots overlap, the ink does not flow or bleed, The diffusion of the dots in the horizontal direction is not unnecessarily large, and the periphery is required to be smooth and unsharp.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to enable authenticity determination by a simple method without requiring a special device.
An object of the present invention is to obtain an ink jet recording sheet having excellent anti-counterfeiting properties.

[0007]

Means for Solving the Problems The present inventors use a paper support on which an optical density is partially formed as a support for an ink jet recording sheet, and provide an ink jet ink receiving layer on at least one surface. As a result, an intended ink jet recording sheet could be obtained.

[0008] The ink jet recording sheet of the present invention may be used as a support for a paper support on which optical density is partially formed, particularly a paper support in which a specific pattern is transparent, or a white paper on a white paper surface. Using a paper support printed with a unique pattern using ink, or a cut colored film piece or a cut metal foil piece, or a multilayered paper support sandwiched between two layers of paper support By providing an ink receiving layer on at least one side thereof, an intended ink jet recording sheet is obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A support partially used in the ink jet recording sheet of the present invention, in which optical shading is partially formed, means that when light is transmitted through the support, the light transmitted through the support is used to determine authenticity. What is necessary is just to provide a sharp shade portion so that specific characters, figures, and the like can be easily visually recognized.
That is, examples of the support include paper, various nonwoven fabrics, woven fabrics, composite paper in which synthetic resin films such as polyethylene terephthalate and polypropylene are bonded, and synthetic paper. In particular, as long as the optical shading is not lost,
Paper laminated with a synthetic resin such as polyethylene or polypropylene, or a composite sheet combining various supports can be used arbitrarily according to the purpose. But,
In consideration of ease of handling as an ink jet recording sheet, ease of disposal, and the like, among these, a support mainly composed of paper is most preferable.

As a method for providing specific characters, figures, and the like for authenticity judgment which can be easily visually recognized by transmitted light on a paper support, a transparent method, in order to keep the surface of the paper support blank, In addition, there is a method of printing a unique pattern on a white paper surface using white ink. In addition, a method of using a paper support in which a cut coloring film piece or a cut metal foil piece is formed, or a multi-layer paper support sandwiched between two layers of a paper support is used to cut a specific shape and size. By using a colored film piece or a cut metal foil piece, the accuracy of visual authentication determination and the difficulty of forgery are excellent.

[0011] Usually, the production of transparent paper is carried out by using a metal net or a synthetic resin thin wire, oil paper, a paper net having characters or figures made of a metal or synthetic resin thin film attached to the surface thereof, or
Attach the mesh for papermaking with the mesh of the characters and figures painted with synthetic resin, etc., as the upper mesh of the cylinder cylinder in the case of a round paper machine, and as the upper mesh of a dandy roll in the case of a fourdrinier machine. This is done by making paper. In any case, the amount of fibers in the characters and figures, that is, the transparent portion, is smaller than that in the non-transparent portion. As a result, when observed with transmitted light, the transparent portion has an optically light bright pattern. Identified as

As the pulp constituting the paper support partially formed with the optical shading used in the present invention, any pulp usually used for papermaking can be used. That is, bleached chemical pulp such as softwood kraft pulp, hardwood kraft pulp, softwood sulphite pulp, and hardwood sulphite pulp, and recycled pulp such as deinked waste paper pulp can be used. Further, mechanical pulp having high whiteness may be used. Furthermore, straw, espat,
Non-wood pulp manufactured from grass fibers such as bagasse and kenaf, bast fibers such as hemp, mulberry, ganpi, and mitsumata, and cotton and the like may be used. Pulp may be used alone, or two or more kinds may be used in combination. However, at the time of the glazing process, in order to sharpen the characters and patterns of the clarification, that is, to rapidly change the thickness of the paper layer in the part where the clarification is performed and the part where the clarification is not performed, the fiber is used. A thinner and shorter one is advantageous.

The pulp is beaten by a beater such as a double disc refiner in order to improve various properties of the paper such as suitability for papermaking, strength, smoothness, uniformity of formation, etc., and clarity of transparency.

The beaten pulp slurry is made by a hand-making method using a paper cage, or by a paper machine such as a fourdrinier paper machine or a round net paper machine. Various additives such as a dispersion aid, a dry paper strength enhancer, a wet paper strength enhancer, a filler, a sizing agent, and a fixing agent of the pulp slurry used at this time can be added as needed. Further, if necessary, a pH adjuster, a dye, a colored pigment, a fluorescent whitening agent and the like can be added.

The dispersing aids include, for example, polyethylene oxide, polyacrylamide, and smelt, and the paper strength enhancers include, for example, vegetable gums, starch, anionic paper strength enhancers such as carboxy-modified polyvinyl alcohol, cationized starch, and the like. Cationic polyacrylamide, a cationic paper strength enhancer such as polyamide polyamine epichlorohydrin resin, as a filler, for example, clay, kaolin,
Examples of the sizing agent include calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, and magnesium hydroxide. Examples of the sizing agent include higher fatty acid salts, rosin, rosin derivatives such as maleated rosin, dialkylketene dimer, alkenyl or alkyl succinate, and epoxy. Fatty acid amide,
Polysaccharide esters, etc., as a fixing agent, for example, aluminum sulfate, polyvalent metal salts such as aluminum chloride, cationized starch, cationic polymers such as polyamide polyamine epichlorohydrin resin, etc., as a PH regulator, hydrochloric acid,
Caustic soda, sodium carbonate and the like are used.

The thickness of the support is not particularly limited as long as the optical density formed on the support can be visually confirmed. The thickness of the support is selected in the range of 20 μm to 300 μm depending on the application.

The paper support partially formed with optical shading for use in the present invention is obtained by a method of printing a unique pattern using white ink on the surface of the support on the side on which the ink receiving layer is provided. In this case, pigments used in the ink include calcined kaolin, kaolin, talc, calcium carbonate, zinc oxide, zinc sulfide, basic lead carbonate, basic lead sulfate, lead sulfate, barium sulfate, lithopone, titanium oxide, antimony oxide, and diatomaceous Earth, aluminum hydroxide, magnesium hydroxide, silica, and inorganic pigments such as alumina,
Organic pigments such as styrene / acrylic resin, polystyrene resin, acrylic resin, polyethylene resin, polypropylene resin, and urea / formalin resin can be used. In addition, inorganic and organic pigments having many pores therein, hollow particles, expandable hollow particles, and air capsules containing air therein can also be used. Among these pigments, zinc oxide, zinc sulfide, basic lead carbonate, basic lead sulfate, lead sulfate, barium sulfate, lithopone,
Titanium oxide, antimony oxide and the like are particularly preferred.

The type of the white ink used in the present invention may be water-based, alcohol-based, or solvent-based. However, from the viewpoint of fire safety, sanitary working environment, reduction of residual solvent after printing, etc. Aqueous inks are preferred. In this case, water is used as the main solvent, and alcohol, cellosolve and the like are used as the co-solvent.

Examples of the binder for the white ink used in the present invention include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylic acid. Ester copolymers, acrylamide / acrylate / methacrylic acid terpolymers, styrene / maleic anhydride copolymer alkali salts,
Water-soluble polymers such as alkali salts of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylate, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer Coalesce, ethylene / vinyl acetate copolymer, ethylene / vinyl chloride copolymer, polyvinyl chloride,
Latexes such as ethylene / vinylidene chloride copolymer and polyvinylidene chloride are exemplified, but not particularly limited thereto. These can be used alone or in combination of two or more. In addition to the above, various additives such as a blue pigment or dye, a dispersant for the pigment, an antioxidant, and an ultraviolet absorber are added in an appropriate combination for the purpose of suppressing yellowing and increasing the apparent whiteness. You can also.

The method of printing the above-mentioned white ink used in the present invention is not particularly limited, and can be performed by a conventional method. For example, various printing machines based on a system such as planographic printing, letterpress printing, intaglio printing, flexographic printing, and screen printing can be used. Among them, it is preferable to use a flexographic printing machine.

The amount and pattern of the white ink used in the present invention are not particularly limited.
What is necessary is that the pattern and the amount of the unique pattern provided by printing can be easily identified as a difference in density when observed by transmitted light.

One type of a multi-layered paper support which is used in the ink jet recording sheet of the present invention and has a cut colored film piece or a cut metal foil piece incorporated in a paper support is a cut colored film at the time of papermaking. It has a three-layer structure in which a paper support is attached to the front and back of a piece of paper into which a small piece or a small piece of cut metal foil has been formed with an adhesive.

Another type of a multi-layered paper support used in the ink jet recording sheet of the present invention, in which a cut coloring film piece or a cut metal foil piece is incorporated into a paper support, is provided on one side of the paper support. A cut coloring film piece or a cutting metal foil piece is applied together with an adhesive, and then a second layer of paper support is pressed thereon, thereby cutting the cutting color film piece or cutting metal sheet between the two layers of paper support. It is manufactured by sandwiching a layer consisting of a foil piece and an adhesive.

The addition of the colored film to the adhesive of the present invention can be carried out by any method such as stirring, continuous administration, or spraying on the adhesive layer.

The term "colored film" as used in the present invention means a film obtained by coloring a resin film or a synthetic fiber and then cutting and subdividing it. Examples of the means for coloring include methods such as dyeing with a dye, kneading and adhering of a pigment, and metal deposition. Among them, those colored white with a white pigment are preferable. The base material of the metal-deposited film is polyester (PET), nylon, polyvinyl chloride, polycarbonate, non-stretched polypropylene, stretched polypropylene, polyethylene, and in some cases, paper, and the like, and the metal to be evaporated is mostly aluminum. But gold, silver,
Copper, chromium, indium, tin and the like are used. The cut metal vapor-deposited film is sometimes called a glitter or a glitter film in a trade name.

The thickness of the colored film is preferably about 4 to 250 μm.
The thickness is more preferably 0 μm, and most preferably 4 to 30 μm in consideration of surface smoothness. If necessary, a protective layer may be provided on the colored film.

The particle size or size of the cut colored film (hereinafter, referred to as cut color film in the present invention) is about 300 mesh (about 50 μm) to about 20 mm, and its shape is square, rectangular, rhombic, or circular. Any shape such as, oval, fibrous, hairy, star-shaped, triangular or irregular may be used. If the size of the cut coloring film is smaller than this range, it becomes difficult to distinguish it with the naked eye, which is not preferable. If it is larger than this range, uniform dispersion and application become difficult, and if it is bent, the portion may become uneven. The cut coloring film is not exactly cut, and may be referred to by the name of spangles, particularly when the cut coloring film is made from a metal-deposited film by a punching method. In the present invention, this is also included in the cut coloring film. As a matter of course, these cut and colored films can be used by mixing various kinds of materials having different sizes, shapes, colors and materials.

When a metal foil is used instead of a colored film, a metal foil such as aluminum, gold, silver, copper, chromium, indium, and tin is used, but is not limited to these metal foils. .

When a metal foil is used, the thickness of the metal foil is preferably about 1 μm to 5 μm, and more preferably about 1 μm in consideration of coating suitability. If necessary, a protective layer may be provided on the metal foil.

The grain size, size and shape of the cut metal foil may be in accordance with the matters described in the section of the cut colored film. Naturally, these metal foils can also be used by mixing various kinds of materials having different sizes, shapes and materials.

In the present invention, the adhesive used for inserting the cut colored film pieces or the cut metal foil pieces between the two layers of paper support is preferably an adhesive or pressure-sensitive adhesive generally used in the paper field. There is no limitation, that is, the adhesive used is a rubber adhesive resin, a synthetic rubber adhesive resin, a modified rubber adhesive resin, a polyvinyl acetate resin adhesive resin, a polyurethane resin adhesive resin, a nitrocellulose adhesive resin, polyester. Resin adhesive resin, urea resin adhesive resin, phenol resin adhesive resin, melamine resin adhesive resin, resorcinol adhesive resin, polyvinyl alcohol adhesive resin, sodium silicate adhesive resin, epoxy resin adhesive resin, cyanoacryl resin Adhesive resin, acrylic resin adhesive resin, silicone resin adhesive resin, unsaturated polyester Fat-based adhesive resin, an ethylene-vinyl acetate-based adhesive resin, polyamide resin adhesive resins, aliphatic or aromatic polyurethane based adhesive resins, such as copolymer nylon-based adhesive resin is used. The application form of the adhesive resin may be an organic solvent-based, aqueous solution-based, emulsion-based, solvent-free, reaction-curable, or hot-melt type. The curing method of the adhesive resin is natural drying, oxidation curing,
Heat curing, addition polymerization, condensation polymerization, heat drying, two-pack curing,
Alternatively, the following radiation curing may be used.

When a cut metal foil having excellent heat resistance is used, it may be mixed with a thermoplastic resin and then applied by melt extrusion.

In the present invention, the electron beam curable resin and the ultraviolet curable resin are collectively referred to as a radiation curable resin. Examples of the radiation-curable resin used as one of the adhesive resins in the present invention include unsaturated polyesters having a radical polymerization-curable functional group at a molecular end or at a molecular side chain, modified unsaturated polyesters, acrylic polymers, and ethylenically unsaturated resins. Polymers having a saturated bond, monomers and the like can be used alone or together with other solvents. The broad classification can be made as follows regardless of the number of radiation-curable functional groups.

(1) Aliphatic, alicyclic, aromatic and araliphatic polyhydric alcohols and (meth) acrylates of (poly) alkylene glycols (2) Aliphatic, alicyclic, aromatic and araliphatic (Meth) acrylate of polyhydric alcohol obtained by adding alkylene oxide to polyhydric alcohol of (3) (poly) ester (meth) acrylate (4) (poly) urethane (meth) acrylate (5) epoxy (meth) acrylate ( 6) (Poly) amide (meth) acrylate (7) (Meth) acryloyloxyalkyl phosphate ester and its salt (8) Vinyl- or diene-based compound having (meth) acryloyloxy group at a side chain or at a terminal (9) ) Monofunctional (meth) acrylate, vinylpyrrolidone, (meth) acryloyl compound (10) ethylenically unsaturated (11) Mono- or polycarboxylic acids having an ethylenically unsaturated bond and their alkali metal salts, ammonium salts, amine salts, etc. (12) Vinyl lactam and polyvinyl lactam compounds (13) Acrylamide compounds (14 ) (Poly) ethers having ethylenically unsaturated bonds and esters thereof (15) Esters of alcohols having ethylenically unsaturated bonds (16) Polyalcohols having ethylenically unsaturated bonds and esters thereof (17) Styrene, divinylbenzene Aromatic compounds having one or more ethylenically unsaturated bonds (18) (Poly) organosiloxane compounds having a (meth) acryloyloxy group at a side chain or at a terminal (19) Silicones having an ethylenically unsaturated bond Compound ( 0) Amino-modified or carbamate-modified (meth) acrylate (21) Multimers or oligoester (meth) acrylate-modified compounds of the above-mentioned compounds (1) to (20) These resins may be used alone. , May be used as a mixture.

The amount of the adhesive applied is not limited, but is preferably in the range of ^{2 to} 30 g / m ^{2 for} the purpose of sufficiently maintaining the adhesive strength with the paper support.

When the amount of the adhesive applied is smaller than this range, sufficient adhesive strength cannot be obtained. The adhesive may be colorless or colored, but is preferably as transparent as possible. The amount of the colored film contained in the adhesive,
Judgment should be made based on the easiness of observation with transmitted light in the state of being sandwiched between two layers of paper support, but it is preferably 0.1 to 3.0% by weight, and approximately 0.5% by weight.
~ 2.0% is more preferred. If the content of the colored film is less than this range, the number of dark-colored parts becomes sparse during observation with transmitted light, making determination difficult. If it is more than this range, the adhesiveness may be reduced.

The electron beam irradiation used for curing the electron beam-curable resin in the present invention has an acceleration voltage of 100 to 1000 KV, more preferably 10 to 1000 KV, from the viewpoint of transmission power and curing power.
It is preferable to use an electron beam accelerator of 0 to 300 KV so that the absorbed dose in one pass is 0.5 to 20 Mrad. If the acceleration voltage or the amount of electron beam irradiation is lower than this range, the penetrating power of the electron beam is too low to perform sufficient curing, and if it is higher than this range, not only does the energy efficiency deteriorate, but also the paper support In addition to decomposition and coloring of adhesives and additives, unfavorable effects on quality such as a decrease in strength appear.

The electron beam accelerator may be, for example, any of an electron curtain system, a scanning type, a double scanning type, and the like.

At the time of electron beam irradiation, if the oxygen concentration is high, the curing of the electron beam-curable resin is hindered. Therefore, replacement with an inert gas such as nitrogen, helium, carbon dioxide or the like is performed to reduce the oxygen concentration to 600 ppm or less. Preferably 40
Irradiation is preferably performed in an atmosphere in which the concentration is suppressed to 0 ppm or less.

In the present invention, the radiation-curable resin can be cured by irradiating an ultraviolet ray, if necessary. Examples of the ultraviolet irradiation device used include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, and the like, and an ozone-less type that generates less ozone. Generally, a plurality of lamps having an output of 80 w / cm or more are used in parallel.

In the present invention, the curing initiator used for curing by ultraviolet irradiation includes acetophenones such as di- and trichloroacetophenone, benzophenone, Michler's ketone, benzyl, benzoin, and the like.
There are benzoin alkyl ether, benzyldimethyl ketal, tetramethylthiuram monosulfide, thioxanthones, azo compounds, and the like, which are selected from the viewpoint of the type of curing reaction of the curable resin, stability, and suitability for an ultraviolet irradiation device. The amount of the curing initiator used is usually in the range of 0.1 to 5% based on the ultraviolet curable resin. A storage stabilizer such as hydroquinone may be used in combination with the curing initiator.

The sensitizer used in the present invention includes aliphatic amines, aromatic group-containing amines, nitrogen heterocyclic compounds,
Allyl urea, O-tolyl thiourea, sodium diethyldithiophosphate, soluble salt of aromatic sulfinic acid, N, N-disubstituted-P-aminobenzonitrile compound, tri-n-butylphosphine, sodium diethylthiophosphate, Michler's ketone , N-nitrosohydroxylamine derivatives, oxazoline compounds, carbon tetrachloride, hexachloroethane, and the like. In general, the curing speed can be improved by using the curing initiator together.

The method of applying the adhesive resin containing the colored film of the present invention includes a gravure coater, a gravure offset coater, a bar coater, a roll coater, an air knife coater, a U comma coater, an AKKU
Coater, smoothing coater, microgravure coater, reverse roll coater, 4 or 5 roll coater, blade coater, dip coater,
Any coater such as a falling curtain coater, a slide coater, a die coater, and a squeeze coater may be used. If the particle size of the colored film is large, a falling curtain coater is suitable.

In the present invention, when using a thermoplastic resin which is melt-extruded as an adhesive tree containing a cut metal foil, any thermoplastic resin generally used for thermoplastic resin coating or thermoplastic resin laminate can be used without limitation. For example, polyethylene (low density, medium density, high density, linear low density polyethylene), polypropylene, polytrimethylpentene, polybutene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, ethylene acrylic acid copolymer, General-purpose melt-extruded resins such as ethylene methyl acrylate copolymer, ethylene vinyl alcohol copolymer, ethylene methacrylic acid copolymer and salts thereof, vinyl chloride, and vinylidene chloride can be used alone or in combination.

In order to integrate a two-layer paper support with a melt-extruded thermoplastic resin containing a cut metal foil,
A general melt extrusion die, a T die, or a multilayer simultaneous extrusion die can be used. As a pretreatment for the melt extrusion, any known treatment for improving adhesiveness such as a corona treatment or a frame treatment may be performed on the paper support. The metal foil can be directly contained in the thermoplastic resin laminate layer, but rather, the metal foil is sprayed on the molten thermoplastic resin on the side in contact with the paper support, or the metal foil is separately coated on the paper support. And a thermoplastic resin may be melt-extruded thereon.

In this case, the surface of the paper support may be subjected to a surface treatment such as a corona treatment, an ozone treatment or a flame treatment in order to improve the adhesiveness and wettability of the paper support. Also,
On the back side of the paper support of the present invention, anti-curl, anti-static,
Alternatively, a backcoat layer such as a water-resistant layer can be provided, and an antistatic agent, a hydrophilic binder, a latex, a hardener, a pigment, a surfactant, an adhesive, etc. are appropriately added to the backcoat layer. Can be.

For the purpose of improving the acceptability of the ink-jet ink, the paper support used in the present invention on which the optical density is partially formed is provided with an ink receiving layer on at least one side. As one mode of providing the ink receiving layer,
An ink jet recording sheet is obtained by performing tab size or size press processing with a liquid containing various additives including a water-soluble polymer additive.

The water-soluble polymer additive used in the present embodiment includes, for example, starch, cationized starch, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, carboxymethyl cellulose, hydroxymethyl cellulose,
Hydroxyethyl cellulose, cellulose sulfate, gelatin, casein, sodium polyacrylate,
Styrene-maleic anhydride copolymer sodium salt, sodium polystyrene sulfonate and the like are used. Further, petroleum resin emulsion, styrene-
Dispersion of ammonium salt of maleic anhydride copolymer alkyl ester, alkyl ketene dimer emulsion, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyethylene, polyvinylidene chloride and the like can be mentioned. As other additives, as an antistatic agent, inorganic electrolytes such as sodium chloride, calcium chloride, sodium nitrate, hydrochloric acid, sodium hydroxide, sodium carbonate and other inorganic electrolytes, glycerin, various surfactants such as polyethylene glycol, clay, It is also possible to use pigments such as kaolin, talc, synthetic amorphous silica, colloidal silica, barium sulfate and titanium oxide, other dyes, and various additives such as fluorescent brighteners in combination.

The ink-jet recording sheet of the present invention, in which the optical density is partially formed, is subjected to size press or tab-size processing with an aqueous solution containing a water-soluble polymer as described above in order to increase the receptivity of the ink-jet ink. However, in order to further improve the receptivity of the ink-jet ink, an embodiment in which an ink-jet ink receiving layer is provided on the surface can be adopted.

In the ink-jet ink receiving layer of the present invention, one or more known pigments can be used in order to improve the ink-absorbing properties of the ink-jet ink and the color reproducibility of the ink-jet ink. For example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, magnesium hydroxide kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth,
Inorganic pigments such as calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, hydrohaloysite, magnesium hydroxide, styrene-based plastic pigment, and acrylic plastic Pigment, polyethylene, microcapsules, organic pigments such as urea resin and melamine resin.

Among the above pigments, as the pigment contained as a main component in the ink-jet ink receiving layer, a porous inorganic pigment is preferable, and porous synthetic amorphous silica, porous calcium carbonate, porous magnesium carbonate, Alumina and the like are mentioned, and porous synthetic amorphous silica having a large pore volume is particularly preferable.

As such synthetic amorphous silica, commercially available ones can be suitably used. For example, Mizukasil P-
526, Mizukacil P-801, Mizukasil NP-8,
Mizukacil P-802, Mizukasil P-802Y, Mizukasil C-212, Mizukacil P-73, Mizukacil P
-78A, Mizukacil P-78F, Mizukacil P-8
7, Mizukacil P-705, Mizukasil P-707, Mizukasil P-707D, Mizukasil P-709, Mizukasil C-402, Mizukasil C-484 (all manufactured by Mizusawa Chemical), Toksil U, Toksil UR, Toksil G
U, Toksil AL-1, Toksil GU-N, Toksil N, Toksil NR, Toksil PR, Solex, Fine Seal E-50, Fine Seal T-3
2, Fine Seal X-37, Fine Seal X-7
0, Fine Seal RX-70 Fine Seal A, Fine Seal B (all manufactured by Tokuyama Soda), Carplex FPS-101, Carplex CS-7, Carplex 80, Carplex XR, Carplex 67
(The above are manufactured by Shionogi & Co., Ltd.), Syloid 63, Syloid 65, Syloid 66, Syloid 77, Syloid 7
4, thyroid 79, thyroid 404, thyroid 6
20, thyroid 800, thyroid 150, thyroid 244, and thyroid 266 (all manufactured by Fuji Silysia Chemical Ltd.).

Examples of the adhesive for the ink-jet ink receiving layer include starch derivatives such as oxidized starch, etherified starch and phosphated starch; cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose; casein, gelatin, soybean protein, and polyvinyl. Alcohols or derivatives thereof; polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, conjugated diene-based copolymer latex such as methyl methacrylate-butadiene copolymer, etc .; polymer or copolymer of acrylate and methacrylate Acrylic polymer latex such as acrylic polymer such as coalescable; vinyl polymer latex such as ethylene-vinyl acetate copolymer; or functional group modification of these various polymers by monomers containing functional group such as carboxy group Polymer latte Water-based adhesives such as thermosetting synthetic resins such as melamine resins and urea resins; acrylic acid esters such as polymethyl methacrylate; polymer or copolymer resins of methacrylic acid esters; polyurethane resins, unsaturated polyester resins, and vinyl chloride -Synthetic resin adhesives such as vinyl acetate copolymer, polyvinyl butyral, and alkyd resin. The amount of the binder is 3 to 70 parts by weight based on 100 parts by weight of the total solids.
If it is less than 3 parts by weight, the coating strength of the ink-jet ink receiving layer will be insufficient, and if it exceeds 70 parts by weight, the ink-jet ink absorption will be reduced.

Further, in the ink-jet ink receiving layer,
As additives, dye fixing agents, pigment dispersants, thickeners, flow improvers, defoamers, foam inhibitors, release agents, foaming agents, penetrants,
A coloring dye, a coloring pigment, a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, a preservative, an antibacterial agent, a waterproofing agent, a wet paper strength enhancer, a dry paper strength enhancer, and the like can also be appropriately compounded.

In particular, secondary amines, tertiary amines and tertiary amines which form insoluble salts with sulfonic acid groups, carboxyl groups, amino groups and the like in water-soluble direct dyes and water-soluble acid dyes, which are dye components of aqueous ink-jet inks. When a cationic dye fixing agent consisting of a quaternary ammonium salt is blended, the dye is captured in the ink receiving layer, so that the color is improved and the formation of an insoluble salt causes the ink to flow out or bleed out due to water dripping or moisture absorption. Is preferred because

In the present invention, if the coating amount of the ink-jet ink receiving layer is too small, not only does the ink-jet ink absorbability deteriorate, but also the image density, color, and sharpness are low, and the ink-jet ink cannot be used. A dot shape called feathering, which is diffused in the plane direction of the layer and jagged like a bird's feather, occurs. In addition, when the coating amount is too large, the drying load in the drying step after coating increases, and not only does the productivity decrease with a decrease in the coating speed, but also the drying under high load constitutes the inkjet ink receiving layer. The adhesive in the coating composition moves to the surface of the ink-jet ink receiving layer together with the solvent that evaporates to reduce the amount of voids on the surface. Therefore, it is not preferable. From such a viewpoint, the coating amount of the inkjet ink receiving layer is preferably from 1 to 30 g / m ² . or,
The ink-jet ink receiving layer can be provided by applying a certain coating amount in several times, and in the case of imparting gloss, the gloss is improved as compared with applying the coating amount at once.

The method for applying the ink-jet ink receiving layer is as follows. Various apparatuses such as a blade coater, a roll coater, an air knife coater, a bar coater, a rod blade coater, a curtain coater, a short dwell coater, and a size press are used on or off. Can be used on machines. Further, after coating, flattening can be performed using a calendar device such as a machine calender, a TG calender, a super calender, and a soft calender.

When the ink-jet ink receiving layer is applied, the ink receiving layer may be provided on the paper support as it is, or a known surface such as a corona treatment, a frame treatment, a plasma treatment, or an ultraviolet irradiation treatment may be applied to the paper support in advance. Processing may be performed.

[0059]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited to these examples. The percentages and parts shown below are% by weight and parts by weight, respectively.

Preparation Example 1 Preparation of Coating Solution for Inkjet Receptive Layer A coating solution for the inkjet receiving layer was prepared according to the following composition. Synthetic amorphous silica (Fine Seal X-37B: manufactured by Tokuyama Soda) 100 parts Polyvinyl alcohol (PVA117: manufactured by Kuraray) 50 parts Cationic dye fixing agent (Smileds Resin 1001: manufactured by Sumitomo Chemical) 20 parts

Example 1 An 80:20 mixture of bleached hardwood kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) was used at a concentration of 4%.
Disperse in water with a double disc refiner,
It was beaten to a freeness of 380 ml with a Canadian Standard Freeness Tester. In this pulp slurry, an alkyl ketene dimer as a sizing agent is 0.15% by weight to pulp, a polyacrylamide is 0.6% by weight to pulp as a strength enhancer, talc is 6% by weight to pulp as a filler, and cationized starch is pulp to pulp. 1.0% by weight was added and diluted with water to obtain a 1% slurry. This slurry was paper-formed using a fourdrinier paper machine to a basis weight of 80 g / m ² using MITSUBISHI (registered trademark) and a dandy roll provided with paper-making characters. Polyfix P60 which is a polycondensate of dimethylamine and epichlorohydrin
1 (manufactured by Showa Polymer Co., Ltd.) was applied with a 0.5% concentration size press solution to obtain an ink jet recording sheet. This ink jet recording sheet has good ink jet ink receptivity, and is "MITSUBISHI" in terms of transmitted light.
Forgery was difficult to counterfeit.

Examples 2 and 3 An 80:20 mixture of bleached hardwood kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) was used at a concentration of 4%.
Disperse in water with a double disc refiner,
It was beaten to a freeness of 380 ml with a Canadian Standard Freeness Tester. In this pulp slurry, an alkyl ketene dimer as a sizing agent is 0.15% by weight to pulp, a polyacrylamide is 0.6% by weight to pulp as a strength enhancer, talc is 6% by weight to pulp as a filler, and cationized starch is pulp to pulp. 1.0% by weight was added and diluted with water to obtain a 1% slurry. This slurry was weighed to 70 basis weight by a fourdrinier paper machine using a dandy roll provided with MITSUBISHI and papermaking characters.
g / m ² , and a size press apparatus was used to press the size of starch oxide at a concentration of 4% to form a support. 5 g of the coating liquid of Preparation Example 1 on this support in terms of dry solid content
/ m ² by using a curtain coater to obtain an ink jet recording sheet of Example 2. Similarly, the coating liquid of Preparation Example 1 was applied so as to have a solid content of 15 g / m ² to obtain an ink jet recording sheet of Example 3.
These inkjet recording sheets have good inkjet ink receptivity, and when viewed in terms of transmitted light, "MITS"
The UBISHI watermark was visible and counterfeiting was difficult.

Examples 4 and 5 ^On a base paper for coating having a basis weight of 65 g / m ² , a white aqueous ink composed of a titanium oxide pigment was subjected to flexographic printing using “MITSUBI”.
"SHI" was printed to produce a support. 5 g / dry solid content of the coating solution of Preparation Example 1 was applied to the printed surface of the support.
m ² was applied by a curtain coater to obtain an ink jet recording sheet of Example 4. Similarly, the coating liquid of Preparation Example 1 was applied so as to have a solid content of 15 g / m ² to obtain an ink jet recording sheet of Example 5.
These inkjet recording sheets have good inkjet ink receptivity, and when viewed in terms of transmitted light, "MITS"
The printing of "UBISHI" appeared as a difference in shading, and forgery was difficult.

Example 6 An 80:20 mixture of bleached hardwood kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP) was used at a concentration of 4%.
Disperse in water with a double disc refiner,
It was beaten to a freeness of 380 ml with a Canadian Standard Freeness Tester. In this pulp slurry, an alkyl ketene dimer as a sizing agent with respect to pulp 0.15% by weight, a polyacrylamide as a strength enhancer with respect to pulp 0.6% by weight, as a colored film,
A polyethylene terephthalate film previously colored white and opaque is 150 μm wide, 12 μm thick, and 2 mm long
1% by weight with respect to pulp and 1.0% by weight of cationized starch with respect to pulp were added and diluted with water to 1%.
% Slurry. A lower layer having a basis weight of 60 g / m ² was formed from the slurry by a circular paper machine, and only the colored film was extracted from the lower layer as an upper layer to form a lower layer having a basis weight of 15 g / m ^2. Created body.
The size press liquid used in Example 1 was applied on the upper layer to ² g / m ² in terms of dry solid content on this support to obtain an ink jet recording sheet of Example 6. This ink jet recording sheet had good ink-jet ink receptivity, and when viewed from transmitted light, small pieces of the cut white opaque film appeared as randomly distributed shadows, making forgery difficult.

Examples 7 and 8 The coating solution of Preparation Example 1 was applied to the support prepared in Example 6 with a curtain coater so that the dry solid content was 5 g / m ² . An ink jet recording sheet was obtained.
Similarly, the coating liquid of Preparation Example 1 was applied so as to have a solid content of 15 g / m ² to obtain an ink jet recording sheet of Example 8. These ink-jet recording sheets had good ink-jet ink receptivity, and when viewed from transmitted light, small pieces of the cut white opaque film appeared as randomly distributed shadows, making forgery difficult.

Examples 9 and 10 As a colored film, one side of a 12 μm thick polyethylene terephthalate film was subjected to aluminum evaporation.
The material cut and subdivided into 150 mesh was used. A high-quality paper made to a basis weight of 30 g / m ² was used as a first layer support, and an emulsion adhesive resin V was used as an adhesive resin.
P-57 (manufactured by Kanebo NS Co.) was mixed with a cut vapor deposition film in an amount equivalent to 1% of the weight before drying, mixed, and then coated with a direct gravure coater to a dry weight of 10 g / m ^2. The same high-quality paper as that used for the first layer was overlaid and dried as a second-layer support to prepare a support. Preparation Example 1
Was applied with a curtain coater so as to have a dry solid content of 5 g / m ² to obtain an ink jet recording sheet of Example 9. Similarly, the coating liquid of Preparation Example 1
What was applied so as to be 5 g / m ² was used as the ink jet recording sheet of Example 10. These ink jet recording sheets have good ink jet ink receptivity,
When viewed with transmitted light, small pieces of the cut vapor-deposited film appeared as randomly distributed shadows, and forgery was difficult.

Examples 11 and 12 As a colored film, one side of a polyethylene terephthalate film having a thickness of 12 μm was subjected to aluminum evaporation.
The material cut and subdivided into 150 mesh was used. As the first-layer support, high-quality paper made to a basis weight of 30 g / m ² was used, and an electron beam-curable resin (a mixture of Aronix M-1310 and M150 in a weight ratio of 6: 4, manufactured by Toagosei Co., Ltd.) was used.
Is mixed with a cut vapor deposition film by an amount equivalent to 1% of the weight before drying, mixed, and then coated with a direct gravure coater so that the dry weight becomes 10 g / m ^{2. As} a second layer support, The same high-quality paper as that used for the first layer is overlaid, and at an accelerating voltage of 200 kV, 2Mr
The resin was cured by irradiating an electron beam from the side of the support so as to have an absorption dose of ad to prepare a support. On this support, the coating liquid of Preparation Example 1 was dried so that the solid content was 5 g / m ² .
It was applied with a curtain coater to obtain an ink jet recording sheet of Example 11. Similarly, the coating liquid of Preparation Example 1 was applied so as to have a solid content of 15 g / m ^{2 in} Example 1.
Inkjet recording sheet No. 2 was obtained. These ink-jet recording sheets had good ink-jet ink receptivity, and when viewed from transmitted light, small pieces of the cut vapor-deposited film appeared as randomly distributed shadows, making forgery difficult.

Examples 13 and 14 As a colored film, a polyethylene terephthalate film which had been colored white and opaque in advance was cut and subdivided into a width of 150 μm, a thickness of 12 μm and a length of 2 mm. Otherwise, the procedure of Example 1 was repeated in the same manner as in Examples 9 and 10.
3, 14 ink jet recording sheets were obtained. These ink-jet recording sheets had good ink-jet ink receptivity, and when viewed from transmitted light, small pieces of the cut white opaque film appeared as randomly distributed shadows, making forgery difficult.

Examples 15 and 16 Polyethylene terephthalate fibers containing titanium were cut to a length of 2 mm and used as colored films. Other than that, the same as in Examples 11 and 12,
Inkjet recording sheet No. 6 was obtained. These ink-jet recording sheets had good ink-jet ink receptivity, and when viewed from transmitted light, small pieces of cut white fibers appeared as shadows randomly distributed, making forgery difficult.

Examples 17 and 18 As a colored film, 1 μm thick aluminum foil was used.
It was cut and divided into irregular shapes of about mm. 1
A high-quality paper made to a basis weight of 30 g / m ² was used as a support for the layer, and cut aluminum foil was mixed in an ultraviolet-curable resin (Aronix UV3400, manufactured by Toagosei Co., Ltd.) as an adhesive resin in an amount equivalent to 1%. Then, after mixing, a direct gravure coater is applied so that the coating amount is 10 g / m ² , and the same high-quality paper as that used for the first layer as a second-layer support is overlaid, Ultraviolet irradiation was performed to cure the ultraviolet curable resin to obtain a support. The coating solution of Preparation Example 1 was applied to this support with a curtain coater so as to have a dry solid content of 5 g / m ² to obtain an ink jet recording sheet of Example 17. Similarly, the coating liquid of Preparation Example 1 was applied so as to have a solid content of 15 g / m ² to obtain an ink jet recording sheet of Example 18. These ink-jet recording sheets had good ink-jet ink receptivity, and when viewed in transmitted light, small pieces of cut aluminum foil appeared as randomly distributed shadows, making forgery difficult.

[0071]

As described above, by using a paper support on which an optical density is partially formed as a support for an ink jet recording sheet, a special light source or the like is not required, and only the transmitted light is used. As a result of being able to determine the authenticity only by observing, it is possible to obtain an ink jet recording sheet having excellent anti-counterfeiting properties and high practicality.

Claims (5)

[Claims] 1. An ink jet recording sheet comprising a paper mainly composed of wood pulp as a support and an ink receiving layer provided on at least one side of the support, wherein the support is partially formed with optical shading. An ink jet recording sheet, characterized in that: 2. The ink jet recording sheet according to claim 1, wherein the optical density of the support is due to penetration during papermaking. 3. The ink jet recording sheet according to claim 1, wherein the optical density of the support is a white ink formed by printing on the surface on which the ink receiving layer is provided before providing the ink receiving layer. . 4. The ink jet recording sheet according to claim 1, wherein the optical density of the support is obtained by cutting colored film pieces or cut metal foil pieces that have been cut during papermaking. 5. The ink jet recording sheet according to claim 1, wherein the optical density of the support is a small piece of cut coloring film or a small piece of cut metal foil sandwiched between two layers of the support.